In general, a gas chromatograph is provided with a sample vaporization unit for vaporizing the sample and feeding the sample to the analysis column. When describing one example of the sample vaporization unit, the sample vaporization unit has a housing, a space serving as a sample vaporization chamber is provided inside the housing, and a sample injection port for injecting the sample into the sample vaporization chamber is provided in the upper part of the housing. The lower part of the sample vaporization chamber is connected to an analysis column, and a carrier gas is introduced from the upper part of the sample vaporization chamber. The sample vaporization chamber is heated to a high temperature, and the liquid sample injected into the sample vaporization chamber is vaporized by heat and sent to the analysis column by the carrier gas.
A cylindrical insert made of quartz glass or the like is accommodated in the sample vaporization chamber inside the housing, and the sample injected from the sample injection port is vaporized inside the insert. Since the sample is configured to be vaporized inside the insert, the sample gas can be introduced into the analysis column, without coming into contact with the metal inner wall of the sample vaporization chamber.
Since the insert is in direct contact with the sample, the insert is a component that is easily stained due to adhesion of vaporized residues of the sample or the like. For this reason, the insert is accommodated in the sample vaporization chamber in a removable state so that the insert can be periodically exchanged or cleaned (see Patent Document 1).
Generally, an opening part communicating with the sample vaporization chamber is provided on the upper surface of the housing, and the opening part is sealed by attaching the seal cap in a state in which the opening part nips the O-ring. The sample injection port for injecting the sample by sticking a sample injecting needle is provided in the seal cap. Inside the seal cap, a septum for closing the sample injection port again after the sample injecting needle has been extracted is provided.
As a structure for attaching the seal cap to the housing, a structure is generally adopted in which a screw provided on the housing side and a screw provided on the seal cap side are screwed together and the seal cap is turned and tightened. However, with such a structure, when replacing the insert, it is necessary to turn the seal cap using a tool such as a spanner. However, since there is a pipe or the like for introducing the carrier gas around the sample injection port, it is difficult to turn the tool, and the task is not easy. Therefore, a mechanism capable of facilitating attachment and detachment of the seal cap without using a tool is desired.
As a mechanism for solving the above problem, a mechanism is suggested in which a protrusion is provided on the housing (a lower assembly) side, an inclined surface for hooking the protrusion of the housing side is provided on the seal cap (upper assembly) side, and the protrusion of the housing side is hooked to the inclined surface of the seal cap side to turn the seal cap and raise the protrusion along the inclined surface, thereby attaching the seal cap to the housing (see Patent Document 2).